Disc herniation and degenerative disorders of the lumbar spine are prevalent, deteriorate the quality of life, and are a major health care concern of the general population.
Lumbar spinal stenosis is defined as the narrowing of the spinal canal in the lumbar region. This is as a consequence of several pathologic conditions, the most common of which is chronic degenerative spondylosis. Other common causes of stenosis include disc herniation, facet hypertrophy, or congenital causes. Absolute stenosis has been defined as a decrease in the midsagittal lumbar canal diameter of less than 10 mm on MRI.
Although there are different ways of describing stenosis, generally the stenosis of the spinal canal can occur centrally or laterally. Patients often present with a combination of symptoms from both central and lateral stenosis.
Lateral stenosis can be further classified into three distinct zones: the lateral recess, foraminal zone, and extraforaminal zone.
Lateral recess stenosis is caused by overgrowth of the superior articular facet, and ligamentum or capsular redundancy or hypertrophy. Foraminal stenosis may be due to a foraminal disk protrusion, posterior osteophyte formation, ligamentum or capsular hypertrophy, or loss of vertical height from degenerative collapse of the disk. The extraforaminal zone, which is defined as the area lateral to the intervertebral foramen, is most often affected by far-lateral disk and osteophyte pathology.
Spinal nerves (also referred to as “nerve roots”) originate from the spinal cord, remain within the central portion of the spinal canal, and then exit through the foramen or neuroforamen. The neuroforamen primarily contains the nerve root exiting from each corresponding intervertebral level. It also contains the dorsal root ganglion (DRG), a structure that contains the cell bodies of the afferent sensory neurons. DRG has a variety of sensory receptors that are activated by mechanical, thermal, chemical, and noxious stimuli. If DRG is impinged within the foramen, in lateral stenosis cases, it can be quite painful, and it can become a major source of pain generation.
Spinal stenosis is treated conservatively initially with therapy modalities and medications. Epidural injections with local anesthetics and steroids may be used next. However, these injections may relieve pain for a limited period of time only. More importantly, injections typically do not influence or improve the functional outcome of patient condition. The majority of patients report little substantial improvement in symptoms with repeated treatment.
Decompression surgery is considered only after conservative treatments have failed. Currently, there are 2 surgical approaches to decompress the lateral portion of the canal: medial (or “inside-out”), and lateral (or “outside-in”, or “transforaminal”). Each has its advantages and disadvantages. The advantage of the medial approach includes surgeon familiarity through a laminotomy. The disadvantage of medial approach is significant bone resection required to get to the foramen, which is located more laterally, and possible dural tear. This excess bone resection may lead to an iatrogenic instability of the spinal segment if it is extensive. Also, trying to reach under the facet to decompress the foraminal zone can result in possible injury to the nerve root injury due to the deep and lateral position of the nerve root within the foramen. The advantage of transforaminal approach includes less or no bone resection, less risk of dural tear, faster recovery due to less muscle dissection, less risk of possible epidural scar formation. The disadvantages of transforaminal approach include technically demanding approach, and difficulty in visualizing the content of foramen from the lateral side.
Balloon dilation is currently used in various parts of the body including esophagus, urethra, coronary arteries, and peripheral arteries. Additionally, balloons have been used to create a void within vertebral body to restore the height of fractured vertebrae and allow for filling of the void with cement or bone graft to stabilize a vertebral fracture, commonly referred to as Kyphoplasty.
Balloons have also been used to aid in separating tissues or vital structures away from a targeted area to be addressed surgically in various parts of the body, including abdominal surgery.
However, the prior art devices or techniques have not addressed the performing a less invasive open or percutaneous decompression of the lateral stenosis through the use of balloons.
The use of balloons in the neuroforamen has been discussed in the prior art, but has not addressed the main problem of having adequate control of the balloon device and the method to specifically localize and target a specific point within the neuroforamen.